Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.31	13.109%	$191.5048	$191.50	$191.50	$191.50
Purchase #2	$59.28	7.771%	$63.8866	$63.89	$63.90	$63.90
Purchase #3	$235.26	11.794%	$263.0066	$263.01	$263.00	$263.00
Purchase #4	$151.84	13.238%	$171.9406	$171.94	$171.95	$171.90
Purchase #5	$167.44	11.236%	$186.2536	$186.25	$186.25	$186.30
Purchase #6	$55.51	13.392%	$62.9439	$62.94	$62.95	$62.90
Purchase #7	$143.46	3.666%	$148.7192	$148.72	$148.70	$148.70
7 purchase totals =	$982.10		$1,088.2553	$1,088.25	$1,088.25	$1,088.20